One of the batteries on the missing Argentine navy submarine short circuited shortly before the boat went missing.

Water entered the snorkel of the submarine and caused one of its batteries to short circuit, an Argentine navy spokesman said Monday.

ARA San Juan, a German-built diesel-electric sub, left the port of Ushuaia on Nov. 8 on a training mission. It has not been seen since and there are fears the 44-member crew has perished after a possible explosion.

Navy spokesperson Enrique Balbi told journalists Monday that the captain had radioed that water had entered through the snorkel when the sub was charging batteries. The water went through the ventilation system to a battery connection tray in the prow and “caused a short circuit and the beginning of a fire, or smoke without flame,” he said.

Balbi said the captain later communicated by satellite phone that the problem had been contained. “They had to electrically isolate the battery and continue sailing underwater to Mar del Plata using another battery circuit,” Balbi said.

Argentine navy officials say the submarine was checked just days before sailing and was deemed to be in good shape and ready for its voyage.

Family members of the crew, however, have told local media outlets the submarine was in poor shape. But Argentina’s navy denies that. “Two days before setting sail, there was a check of the whole operating system,” Balbi told journalists on Saturday. “The submarine doesn’t sail if that’s not done. If it set off from Ushuaia, it was because it was in condition to do so.”

The navy stated that the sub’s captain reported on Nov. 15 he was dealing with a battery problem. The captain, however, later told navy officials via satellite phone that the problem had been fixed and the boat would operate submerged and would continue heading towards the port of Mar del Plata.

Search efforts are still continuing.

The San Juan, a German-built diesel-electric TR-1700 class submarine was commissioned in 1985 and was most recently refitted in 2014.